• Definition
    • restricted lung expansion
    • results in reduced lung volumes (TLC and FVC)
  • Pathophysiology
    • poor breathing mechanics with normal lung function
      • muscle weakness
        • polio and myasthenia gravis
      • chest wall limitation
        • kyphosis, scoliosis, and morbid obesity
      • ↓ pleural compliance
        • mesothelioma
    • interstitial lung diseases (diffuse parenchymal lung disease - DLCO)
      • results in reduced lung compliance and increased elastic recoil 
      • the primary mechanism of resting hypoxemia in patients with interstitial lung disease is V/Q mismatch, with DLCO defect contributing to hypoxemia with activity
      • increased expiratory flow rates due to increased radial traction (result of increased elastic recoil) on airway walls
        • prevents small degree of dynamic collapse of conducting airways found in normal lungs 
      • results in ↓ in lung compliance and ↑ elastic recoil
        no relative change in ventilation/perfusion because capillaries are destroyed along with alveolar units
      • types
        • acute
          • acute interstitial pneumonia (AIP)
            • presents similar to acute respiratory distress syndrome (ARDS)
          • neonatal respiratory distress syndrome
          • drug toxicity (bleomycin, busulfan, and amiodarone)
        • chronic
          • idiopathic interstitial pneumonias
            • most common is idopathic pulmonary fibrosis (IPF)
            • non-specific interstitial pneumonia, respiratory bronchiolitis, desquamative interstitial pneumonia, cryptogenic organizing pneumonia, and lymphocytic interstitial pneumonia
          • pneumoconioses
            • coal miner's
            • silicosis
            • asbestosis
          • sarcoidosis
            • may also show obstructive or mixed pattern on PFT's
          • pulmonary Langerhans cell histiocytosis
          • hypersensitivity pneumonitis (may be acute, subacute, or chronic)
          • lymphangiomyomatosis (primarily young women)
  • Pulmonary function tests
    • FEV1 sec/FVC ratio should be normal
      • approximately normal because both FEV1 sec and FVC are reduced
    • ↓ FVC and TLC
      • key finding for restrictive lung diseases (TLC must be reduced)

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